[flang] [llvm] [mlir] [flang][OpenMP] Add frontend support for ompx_bare clause (PR #111106)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

> I guess a semantics check for it would also be in order.

I actually tried to implement the semantic check for ompx_bare a while back before I realized that the parser doesn't handle it.  I might still have that code lying around somewhere.  We should include the corresponding check in clang as well.  I'll try to add a commit to this PR with these changes.

https://github.com/llvm/llvm-project/pull/111106